Buckingham Palace has become part of a small but fast-growing trend that is redefining the century-old conception of lighting, replacing energy-wasting disposable bulbs with semi-permanent light-emitting diodes, or LEDs.

The new lights are expected to last more than 22 years and enormously reduce energy consumption and carbon dioxide emissions – a big plus for Prince Charles, an ardent environmentalist. Over the past two years, the palace has installed the lighting in chandeliers and on the exterior, where illuminating the entire facade uses less electricity than running an electric teakettle.

A recent report by McKinsey & Co. cited conversion to LED lighting as potentially the most cost-effective of a number of simple approaches to tackling global warming using existing technology.

Studies suggest that a complete conversion to the lights could decrease carbon dioxide emissions from electric power use for lighting by up to 50 percent in just over 20 years; in the United States, lighting accounts for about 6 percent of all energy use.

LED lighting was once relegated to basketball scoreboards, cell phone consoles, traffic lights and colored Christmas lights. As a result of rapid developments in the technology, it is poised to become a staple on streets and in buildings, as well as in homes and offices. Some American cities, including Ann Arbor, Mich., and Raleigh, N.C., are using the lights to illuminate streets and parking garages, and dozens more are exploring the technology. The lighting adorns the conference rooms and bars of some Renaissance hotels, a corridor in the Pentagon and a new green building at Stanford University.

LEDs are more than twice as efficient as compact fluorescent bulbs, now the standard for greener lighting. Unlike compact fluorescents, LEDs turn on quickly and are compatible with dimmer switches. And while fluorescent bulbs contain mercury, which requires special disposal, LED bulbs contain no toxic elements and last so long that disposal is not much of an issue.

“It is fit-and-forget lighting that is essentially there for as long as you live,” said Colin Humphreys, a researcher at Cambridge University who works on gallium nitride LED lights, which now adorn structures in Britain, including the massive Severn Bridge.

The switch to LEDs is proceeding far more rapidly than experts had predicted just two years ago. President Barack Obama's stimulus package, which offers money for green infrastructure investment, will accelerate that pace, experts say. San Jose plans to use $2 million in energy-efficiency grants to install 1,500 LED streetlights.

Thanks in part to the injection of federal cash, sales of the lights in new “solid state” fixtures – a $297 million industry in 2007 – are likely to become a near-billion-dollar industry by 2013, said Stephen Montgomery, director of LED research projects at ElectroniCast, a California consultancy. After years of resisting what they had dismissed as a fringe technology, even giants such as General Electric and Philips have begun making LEDs.

Although the U.S. Department of Energy calls LEDs “a pivotal emerging technology,” significant barriers remain. Homeowners may balk at the high initial cost, which lighting experts say will take five to 10 years currently to recoup in electricity savings. An outdoor LED spotlight today costs $100, as opposed to $7 for a regular bulb.

Another issue is that LEDs now provide only “directional light” rather than a 360-degree glow, meaning they are better suited to downward-facing streetlights and ceiling lights than to many lamp-type settings.

And in the rush to make cheaper LED lights, poorly manufactured products could erase the technology's natural advantage, experts warn. LEDs are tiny sandwiches of two different materials that release light as electrons jump from one to the other. The lights must be carefully designed so that heat does not damage them, reducing their life span from decades to months.

Brian Owen, a contributor to the trade magazine LEDs, said that while it is good that cities are exploring LED lighting: “They have to do their due diligence. Rash decisions can result in disappointment or disaster.”

At the same time, nearly monthly scientific advances are addressing many of the problems, decreasing the price of the bulbs somewhat and improving their ability to provide normal white light bright enough to illuminate rooms and streets.

“This is a technology on a very fast learning curve,” said Jon Creyts, an author of the McKinsey report, who predicted that the technology could be in widespread use within five years.

So far, the use of LEDs has been predominantly in outdoor settings. Toronto, Raleigh, Ann Arbor and Anchorage – not to mention Tianjin, China, and Torraca, Italy – have adopted LEDs for street and parking garage lighting, forsaking the yellow glow of traditional high-pressure sodium lamps. Three major California cities – Los Angeles (140,000 streetlights), San Jose (62,000) and San Francisco (30,000) – have embarked on some LED conversions.

Nonetheless, the lights are also rapidly moving indoors, where they could have an enormous effect on climate change. About 20 percent of carbon dioxide emissions associated with buildings in the United States and the United Kingdom is related to indoor lighting; in some houses the number is as high as 40 percent.

Buoyed by the improvements in the technology, Peter Byrne, the lighting designer and energy consultant for Buckingham Palace, installed the 32,000 custom LEDs in the ceiling of the grand stairwell when older fixtures wore out.

He estimates that half of lights in homes, and particularly those in offices and stores, can already be replaced by LEDs.

“At this point LEDs can't be used in all lights, but that's changing every month,” Byrne said. “If you go into Wal-Mart and look at all those twin 8-foot fluorescents above every aisle, you realize that the potential is enormous.”